#include <math.h>
#include <iostream>
using std::cout;
using std::endl;

class Point{
public:
    Point(int x = 0,int y = 0)
    : _ix(x)
    , _iy(y)
    {
        cout << "Point(int,int)" << endl;
    }
    
    //友元声明
    friend
    float distance(const Point & lhs,const Point & rhs);
private:
    int _ix;
    int _iy;
};

//友元的普通函数形式
float distance(const Point & lhs,const Point & rhs){
    return sqrt(pow(lhs._ix - rhs._ix,2) + pow(lhs._iy - rhs._iy,2));
}

void test0(){
    Point pt1(0,0);
    Point pt2(3,4);
    cout << distance(pt1,pt2) << endl; 
}

int main(void){
    test0();
    return 0;
}
